For many years, combustion engines were controlled in a very simple way: the accelerator pedal was mechanically linked to a butterfly valve in a carburetor, which controlled the air/fuel flow into the engine. While this was an inexpensive and generally reliable approach, it was very inefficient and imprecise. Carbureted and diesel engines often ran at sub-optimal levels, consuming more fuel, producing poorer emissions, and generating fewer horsepower than they were designed to.
Today, carbureted and diesel engines have almost exclusively been replaced with electronically controlled, fuel-injected engines because of the improvements in fuel consumption, emission production and power generation. A simplified block diagram of such a control system is presented in FIG. 1. In this diagram, the engine control unit 12 (ECU), receives input signals from the accelerator pedal 14 and a variety of other sensors 16, and processes the data it receives to generate signals which control the engine's fuel injectors 18 and a variety of other actuators 20.
The ECU 12 itself, typically consists of a micro-controller or microcomputer which has a central processing unit (CPU), read only memory (ROM), random access memory (RAM) and other support logic, which are used to execute-a stored control program.
The accelerator pedal 14 is mechanically connected to an accelerator position sensor 22 for detecting the position of the accelerator pedal 14. Thus, the position of the accelerator pedal 14 is converted to an electrical signal which is transmitted to the ECU 12. Note that the accelerator pedal 14 is normally biased upwards by a spring.
The nature of the sensors 16 may vary widely with the vehicle make, model and year. In general though, these sensors 16 may include manifold absolute pressure, mass air flow, engine speed, manifold charge temperature, exhaust gas recirculation flow, exhaust fuel/air ratio, coolant temperature sensor, vehicle speed, oxygen and other sensors.
With this data, the ECU 12 can perform calculations to determine the optional ignition and fuel conditions. The outputs are sent to the engine via the fuel injectors 18 and the other actuators 20. The group of actuators 20 may include, for example, various warning lights for the driver, exhaust gas recirculation valves and ignition coils.
Now, there are a number of scenarios in which end users may wish to modify this complex control system. In mining applications, for example, diesel trucks may be used underground. If the horsepower (hp) that a truck is producing is sufficiently low, then it can operate freely. However, if the power production of the truck is too high, workers must stop working in the area so they can avoid the truck's emissions (as well, air consumption is directly related to horsepower). Thus, there is a demand for a power modifying feature in trucks and other combustion engine vehicles.
Other applications for such a power modifying feature might include a traction control option for a truck or sportslutility vehicle (SUV), or a power limiter for a tour vehicle or float in a parade.
While technologically, vehicles could be manufactured with a modifiable throttle control system, there is not enough demand to justify the extraordinary expense automobile and truck manufacturers would face in providing this as an option. The cost of altering their assembly lines, parts supply and other manufacturing processes would be enormous and at the present, the manufacturers cannot justify these costs. Thus, any such system would have to be provided as an after-market option.
In many cases, the performance of the engine can be altered by replacing a pre-programmed integrated circuit in the ECU 12. However, programming a new integrated circuit is not straightforward as the operation of the ECU 12 is completely proprietary and very complex. Any mistakes could easily damage the engine or cause the engine emissions to fall outside of regulatory guidelines. As well, many different integrated circuits would have to be programmed to maintain a fleet of vehicles as the programming requirements generally vary with the make, model, year, transmission, engine and other specifications of the vehicles. The use of pre-programmed integrated circuits is therefore an expensive and impractical solution to the problem.
Speed limiters are known in the engine industry and are often, for example, used to prevent diesel generators from damaging themselves by rotating too quickly. Such over-speed preventors typically consist of an RPM sensor (rotations per minute sensor) and control circuit which advises an alarm condition and cuts off the ignition and/or fuel to the engine. These systems are complex, relatively expensive, and the installation of such a system as an after-market item would also be complicated and expensive. More important, such systems do not assist in limiting the power, but merely shut the engine off when a limit is exceeded. It would be very difficult to modify such a system to limit the power of the engine as such systems have no modulating ability, or interface with the engine system which would allow such modulation to take place.
There is therefore a need for a low cost power modifier for trucks and automobiles which can be sold and installed as an after-market product. This design must be provided with consideration for performance, reliability, purchase price, and the cost and difficulty of installation.